Injection Molding Converter DC Link Voltage Control
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Solution Overview
Problem
Injection molding machines face challenges in maintaining desired energy levels in the DC link without upsizing the converter, as energy requirements vary across different processes in the molding cycle, leading to potential energy accumulation issues during regenerative and powering modes.
Innovation Solution
The injection molding machine employs a power supply converter with a second electric power converting part that synchronizes with the phase of the power supply to generate regenerative energy and a controller that adjusts the DC link voltage to a target value, ensuring energy is maintained at the desired level by boosting the voltage during high-power operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power transistors of the converter are always driven to supply electric power necessary for the motor based on the electric power from the power supply, then the energy supply reliability is improved, but the converter size increases
Solution Approach 1:
The patent applies dynamics by making the converter operation mode variable rather than fixed. The control apparatus dynamically switches between powering mode and regenerative mode based on real-time DC link energy levels and motor operating conditions. This dynamic adaptability allows the system to maintain reliable energy supply while avoiding the need for an oversized converter that would be required if it operated continuously in powering mode.
Solution Approach 2:
The patent changes the operational parameters of the converter by switching between two distinct operating modes: powering mode (converting AC to DC) and regenerative mode (converting DC to AC). The control apparatus adjusts the converter's function based on energy accumulation in the DC link, allowing the same hardware to serve different purposes at different times, thereby avoiding the need for an oversized converter designed for continuous powering operation.
2Loss of energy
If the converter operates in regenerative mode only when DC link voltage exceeds upper limit, then the energy accumulation problem is solved, but the energy availability for high-power processes is insufficient
Solution Approach 1:
The control apparatus performs preliminary action by proactively managing DC link energy accumulation before high-power processes occur. It monitors energy levels and switches to regenerative mode in advance to maintain optimal energy levels, ensuring that sufficient energy is available when needed for injection or mold opening/closing processes, rather than waiting for voltage to exceed limits.
Solution Approach 2:
The system implements feedback control by continuously monitoring the DC link voltage and energy levels, then adjusting the converter's operation accordingly. The control apparatus uses this feedback to determine when to switch between powering and regenerative modes, ensuring that energy levels are maintained within optimal ranges to support high-power processes while preventing excessive voltage accumulation.
3Stability of the object's composition
If the converter size is increased to maintain desired energy levels, then the energy supply stability is improved, but the device complexity and cost increase
Solution Approach 1:
The system applies self-service by using the converter itself to manage DC link energy levels through regenerative operation. Instead of requiring additional external energy storage devices or larger converter capacity, the converter serves dual purposes: powering the motor and regenerating energy back to the DC link. This self-managing approach maintains energy supply stability without increasing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for consistent energy supply during high-power operations without upsizing the converter, ensuring that energy is maintained at the desired level, enabling efficient and reliable injection molding processes.
Implementation Method 1
the converter includes a single power converting part (a bridge circuit) which is comprised of power transistors and diodes which are connected to the corresponding transistors with inverse-parallel connections. The disclosed converter converts three-phase supplied power to DC electric power with full-wave rectification by the diodes
Implementation Method 2
it drives the power transistors in synchronization with a phase of the three-phase supplied power to generate regenerative electric power to be charged in the power supply at the time of a motor regenerating mode
Data Source
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AI summary
An injection molding machine is disclosed which includes a converter (100) configured to convert electric power from a power supply (200) and supply the converted electric power to a motor (11, 24, 42, 44) via a DC link (300); and a control apparatus (26) configured to control the converter (100) for molding at a predetermined molding cycle. The converter (100) is capable of operating in a forward direction to output the converted electric power to the DC link (300), and in a backward direction to output a converted regenerative electric power of the motor (11, 24, 42, 44) to the power supply (200). The control apparatus (26) instructs the converter (100) to operate in the forward direction in a predetermined time period in the molding cycle such that a voltage of the DC link (300) becomes a predetermined target voltage.